The paratrooper's heads were preserved to be displayed in Nazi museums.

Campaigners are calling for the Czech Republic to give a heroes' funeral to two paratroopers who assassinated one of the chief architects of the Holocaust – high-ranking Nazi Reinhard Heydrich –during the Nazi occupation of Czechoslovakia.

Ján Kubiš and Josef Gabcík were trained in Britain prior to the attack, which saw Gabcík throw a grenade into Heydrich's car while he was on his way to work in Prague. At the time, the Nazi leader controlled Nazi-occupied Bohemia and Moravia.

The assassination led to a spate of reprisal killings, including almost all the inhabitants of the villages of Lidice and Lekazy, according to the Observer.

Kubiš and Gabcík hid in a Prague cathedral before they were found – but they, along with five other resistance fighters, committed suicide rather than allow themselves to be captured.

The assassins' heads were said to have been put in pickle jars to be shown in a Nazi museum but went missing after the war. Their bodies are thought to have been dumped in unmarked graves in Prague's Ďáblice cemetery.

Neela Winkelmann from the European Platform of Memory and Conscience in Prague told the newspaper: "In Britain and France, Resistance fighters are treated with the utmost respect. Ours are in mass graves and people are turning away from them.

"It's disrespectful what we have done to Gabcík and Kubiš. They killed the only Nazi leader to be assassinated in the war, and he just happened to be one of the main architects of the Holocaust."

Campaigners also say that the fact that Gabcík and Kubiš were trained in the UK affected how the subsequent Communist regime treated their legacies: "If they had come from Russia they would have made big heroes of them. But they came from Britain and many of the political prisoners after the Communists took control in 1948 had been former army men with the Resistance based in England."